1. Field of the Invention
This invention relates to an electromagnetic release shutter and more particularly to an improvement in the locking mechanism of the shutter arranged to lock it in a charged state when it is charged into an initial position thereof.
2. Description of the Prior Art
The locking mechanism of an electromagnetic release type shutter in general has locking members which are arranged to accumulate the energy of shutter blade driving springs in response to a shutter charging action and to lock the driving springs as well as releasing mechanisms which are arranged to release the driving springs from their locked states by operating the locking members through the actions of electromagnets. To obtain stable precision of an electromagnetic release shutter of this type, it has been considered necessary to arrange the locking members, etc. to reduce the releasing torque required so that the locking effected by the locking members can be removed by a force as light as possible. Such an arrangement on the other hand tends to unintentionally have the shutter unlocked causing the shutter blades to travel as the result of a shock inflicted thereon, for example while the camera for which the shutter is used is carried. Therefore, in order to prevent such undesirable occurrences for reliable shutter operations, the torque required for release from locking members must be set to be higher than a certain minimum value.
Accordingly, there has been a limit to the degree of reduction of the releasing torque for the locking members used in the conventional electromagnetic release type shutters. Since some safety allowance must be additionally taken into consideration in determining the releasing torque for the locking members and the locking mechanism, it has been impossible to obtain stable precision of shutters. This has caused many inconveniences in the practical applications of the conventionally known arrangement. Further, in order to cope with the additional portion in the releasing torque of the locking members and the locking mechanism, the conventional electromagnetic release type shutters have necessitated either an increase in the size of electromagnets to be used for operating the locking members or an increase in the operating forces of the electromagnets by supplying a larger current thereto. This has resulted in increase in the size of the shutter.